Elecraft › [K3]

[K3] Variable filters? And what filter is best for AM broadcast reception?

Classic

List

Threaded

6 messages Options

Thomas Horsten

[K3] Variable filters? And what filter is best for AM broadcast reception?

Hi,

I read somewhere, some time ago, that there was a plan to introduce variable
filters to the K3.

Do any such filters exist, either as 3rd party mods or official by
Elecraft/Inrad? And is there any firmware support for this?

I already have 2*2.7kHz and 2*500Hz in my K3, plus a 2.1kHz in the main
receiver only, but I would like a wider filter for AM-broadcast SWL and AM
TX/RX.

Also, I would like to listen to shortwave broadcast stations so I was
planning to get the KBPF3 and additional filters. As far as I can tell the
best filter for this would be KFL3B-FM, to capture the wide signals of the
broadcast stations in the highest possible quality, is that correct or is
the KFL3A-6K more useful? And can I transmit 6kHz AM with the 13kHz FM
filter or must I have the 6kHz one as well?

73, Thomas M0TRN
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: [K3] Variable filters? And what filter is best for AM broadcast reception?

Thomas,

As I recall, the variable filter concept has been dropped. Even if it
were to be available, it would be only a narrow filter, not a wide one.

The 13 kHz filter can be used for FM transmit and receive, but only for
AM receive - you must have the 6 kHz filter for AM transmit. The folks
at Elecraft are reluctant to allow the 13 kHz filter to be used for AM
transmit because of the potential for spurs. A couple of users have
reported here on the reflector that they have "lied" to the K3 about the
filter width and tried it, but I am not certain how rigorously that
setup was tested.

So the bottom line is that you need the real 6 kHz filter to transmit AM
or ESSB. The 13 kHz filter will work nicely for AM receive, although
synchronous AM reception can be used with just as wide an audio
passband, so you might want to investigate that approach and get the 6
kHz filter if you do not anticipate using FM.

73,
Don W3FPR

On 5/13/2011 6:06 AM, Thomas Horsten wrote:

> Hi,
>
> I read somewhere, some time ago, that there was a plan to introduce variable
> filters to the K3.
>
> Do any such filters exist, either as 3rd party mods or official by
> Elecraft/Inrad? And is there any firmware support for this?
>
> I already have 2*2.7kHz and 2*500Hz in my K3, plus a 2.1kHz in the main
> receiver only, but I would like a wider filter for AM-broadcast SWL and AM
> TX/RX.
>
> Also, I would like to listen to shortwave broadcast stations so I was
> planning to get the KBPF3 and additional filters. As far as I can tell the
> best filter for this would be KFL3B-FM, to capture the wide signals of the
> broadcast stations in the highest possible quality, is that correct or is
> the KFL3A-6K more useful? And can I transmit 6kHz AM with the 13kHz FM
> filter or must I have the 6kHz one as well?
>
> 73, Thomas M0TRN
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Craig Smith

Re: [K3] Variable filters? And what filter is best for AMbroadcast reception?

In reply to this post by Thomas Horsten

Good Morning Thomas ...

The variable BW filter concept was pitched early on - before the K3 was
first produced. But nothing has come of it, so don't hold your breath.
Even if it does materialize, it probably wouldn't cover an extremely broad
range, such as 10 KHz to CW widths.

So go ahead and purchase either the 6 KHz or the 13 KHz for SW and BCB AM
listening. For this purpose, the 13 KHz is better as you point out. That
is what I use. But if you plan on transmitting on AM you will need the 6
KHz filter.

73 Craig AC0DS

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Barry N1EU

Re: [K3] Variable filters? And what filter is best for AMbroadcast reception?

Craig D. Smith wrote

For this purpose, the 13 KHz is better as you point out.

FWIW, I directly compared the 6Khz and 13Khz filters on AM receive in my K3, which has the latest dsp updates (includes a 4Khz low pass audio filter). The a.m. receive audio passband was 4Khz wide with either filter. The 13Khz filter did not provide wider audio as expected in my K3.

Barry N1EU

Joe Subich, W4TV-4

Re: [K3] Variable filters? And what filter is best for AMbroadcast reception?

> The a.m. receive audio passband was 4Khz wide with either filter.
> The 13Khz filter did not provide wider audio as expected in my K3.

Unless your AM filter is significantly wider than the published 6 KHz
or you are using the Sync detector with the IF filter offset for one
sideband, the AM filter can not produce a flat audio response to the
full 4.2 KHz allowed by the DSP with the added analog lowpass filter,

If the AM filter is doing its job (based on the published selectivity
at: http://www.elecraft.com/K3/K3_8_pole_plots.htm) and the filter is
centered on the carrier frequency, the audio response should be down
by nearly 40 dB at 4 KHz compared to response at 3 KHz.

73,

... Joe, W4TV

On 5/13/2011 9:34 AM, Barry N1EU wrote:

>
> Craig D. Smith wrote:
>>
>> For this purpose, the 13 KHz is better as you point out.
>>
> FWIW, I directly compared the 6Khz and 13Khz filters on AM receive in my K3,
> which has the latest dsp updates (includes a 4Khz low pass audio filter).
> The a.m. receive audio passband was 4Khz wide with either filter. The 13Khz
> filter did not provide wider audio as expected in my K3.
>
> Barry N1EU
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K3-Variable-filters-And-what-filter-is-best-for-AM-broadcast-reception-tp6358819p6359445.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Matt Zilmer

Re: [K3] Variable filters? And what filter is best for AMbroadcast reception?

In reply to this post by Thomas Horsten

It's a tradeoff. 13 KHz gets you FM capability on TX, but should not
be used for AM. The 6 KHz filter is adequate for SWL and allows AM
TX.

Personally, I have no need for AM TX, so using the 13 KHz filters (one
in each RX), also allowing regular FM on TX/RX. This is useful if you
have the K144XV 2m transverter. The 13 KHz filters work fine for AM
RX. Because I operate on MARS freqs, the KBPF3 is also a necessary
ingredient and I have one on both receivers. Same thing for you to
use in SWL work. Your only limitation is reduced sensitivity around
the 8.2 MHz IF, and TX is hard-locked out from 7.5 to 9.0 MHz. The K3
RX also won't show the specified sensitivity in between ham bands,
when the KBPF3 is in use.

The KBPF3 doesn't give the front end protection that the bandpass
filters do, but it gives you at least reasonable sensitivity between
the ham banads.

73,
matt W6NIA

On Fri, 13 May 2011 11:06:52 +0100, you wrote:

>Hi,
>
>I read somewhere, some time ago, that there was a plan to introduce variable
>filters to the K3.
>
>Do any such filters exist, either as 3rd party mods or official by
>Elecraft/Inrad? And is there any firmware support for this?
>
>I already have 2*2.7kHz and 2*500Hz in my K3, plus a 2.1kHz in the main
>receiver only, but I would like a wider filter for AM-broadcast SWL and AM
>TX/RX.
>
>Also, I would like to listen to shortwave broadcast stations so I was
>planning to get the KBPF3 and additional filters. As far as I can tell the
>best filter for this would be KFL3B-FM, to capture the wide signals of the
>broadcast stations in the highest possible quality, is that correct or is
>the KFL3A-6K more useful? And can I transmit 6kHz AM with the 13kHz FM
>filter or must I have the 6kHz one as well?
>
>73, Thomas M0TRN
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html